Presently, when air bag covers are provided in automobiles on the driver's side of the vehicle, the air bag is stored in the steering column behind an air bag cover. During automatic inflation of the air bag, the air bag cover moves away from the steering column to permit the air bag to perform its safety function between the steering column and the operator of the vehicle.
Recent practice in the automotive industry is utilization of all plastic fabricated air bag covers. Conventional air bag covers used in conjunction with occupant restraint systems often include various switches such as horn switches.
U.S. Pat. No. 5,371,333 discloses a steering wheel pad with a horn switch assembly. A plurality of ribs are integrally formed on a bottom surface of an outer member. The ribs abut with the top surface of an inner member on the top surface of a switch body of a horn switch. When the outer member is not pressed, the ribs maintain the outer member in a predetermined shape. When the outer member is pressed, the ribs transmit the pressure to the switch body.
U.S. Pat. No. 5,085,462 issued to Gaultier discloses an air bag and vehicle horn switch assembly. Gaultier also discloses a conventional two-piece cover construction.
U.S. Pat. No. 5,186,490 issued to Adams et al. discloses a cover or an inflatable restraint system for a motor vehicle which contains a slot in the upper wall thereof into which a replaceable thin or membrane-type switch assembly is inserted.
The Embach U.S. Pat. No. 4,934,735 discloses a device which has inner and outer covers or plates, each of which has split lines which separate the upper walls into upwardly and oppositely opening upper and lower pairs of flaps to permit deployment of the inflatable cushion. A switch assembly is located between either or both pair of flaps and includes one or more membrane switches located between the flaps and respective key pads projecting outwardly of the cover flap for closing respective pairs of circuits on the upper and lower flexible membranes of the membrane switch to each other.
The Heidorn U.S. Pat. No. 5,308,106 discloses an air bag module cover assembly with a switch subassembly removably attached at a front surface of the assembly.
The Winget U.S. Pat. No. 5,062,661 discloses a rigid plate attached to the substantially rigid remainder of a front panel of an air bag cover to define a hollow compartment which together move upon manual actuation of a flexible, manually operable diaphragm at the front surface of the front panel. The front panel has a first electrically conductive inner surface for making a circuit path with a corresponding second electrically conductive inner surface of the rigid plate.
The Cooke, II U.S. Pat. No. 5,344,185 discloses an air bag cover having a replaceable horn switch and a removable cover band.
The Leonelli U.S. Pat. No. 5,369,232 discloses a membrane horn blow switch integrated into the front panel of an air bag cover. More specifically, the membrane switch seats in and fills a horn actuation area which is a step-down portion of the cover reduced in thickness.
The U.S. patent to Hayashi et al. 5,198,629 discloses a steering wheel having an insert molded membrane switch.
The U.S. patent to Inoue et al. 5,338,059 discloses an air bag cover including a horn switch.
The U.S. patent to Trojan et al. 5,499,841 discloses a housing assembly for an air bag and a vehicle horn switch.
The U.S. patent to Margetak et al. 5,639,114 discloses an air bag cover having a plurality of force concentrators which cooperate with projections of a horn switch to concentrate force applied to the cover.
The U.S. patent to Bowman et al. 5,642,901 discloses a relatively flexible thermoplastic air bag cover including a front panel wherein switch activating members enhance activation of a membrane-type switch located at a switch location area of the front panel. This feature provides pressure points which enhance activation of the membrane-type switch. The switch activating members are located on the rear inner surface of the cover in one embodiment and, in another embodiment, on the upper surface of a back plate which provides a hollow compartment for the switch. The switch activating members can be integrally formed in the shape of small circles, ribs, raised dots, X's, etc.
The U.S. patent to Kauer 5,685,561 discloses a relatively flexible thermoplastic air bag cover assembly having a switch and method of manufacturing same including a thermoplastic electromagnetic material which forms welds between front and back panels of the assembly. The welded front and back panels define a switch pocket therebetween to hold the switch such as a membrane-type horn switch therein. The welds occupy a relatively small amount of surface area yet provide strong polymer-to-polymer linkages between the front and back panels, thereby enlarging the effective switch activation area on the outer surface of the front panel. The welds are located very close to the switch pocket without damaging the switch during manufacturing. The bonds provided by the welds between the front and back panels are strong enough to prevent the switch from exiting the switch pocket during air bag deployment.
One problem associated with some of the prior art is that the inner surface of the front panel of the cover has projections formed thereon to facilitate switch activation. These projections, however, present problems in that: the mold is relatively complicated in construction, the cover tends to stick to the mold surface, the outer surface of the front panel is a Class "A" surface which is effected by such difficulties, and each cover often requires specialized tooling.